[Plasmids of incompatibility group H among multiresistant "Salmonella" (author's transl)]. / Plasmides du groupe d'incompatibilité H chez des souches de Salmonella multirésistantes.

A total of 449 multiresistant strains of Salmonella recently isolated from human beings and animals in France and in Belgium and belonging to 21 serotypes, were screened for the presence of IncH R plasmids. These plasmids were identified in 236 strains belonging to 14 different serotypes: mainly S. typhimurium, S. schwarzengrund and S. saint-paul, but not in S. dublin nor S. kedougou. The IncH R plasmids confer resistance to four or more drugs and to tellurium compounds. The properties of 14 plasmids were studied by genetic methods and agarose gel electrophoresis following digestion with EcoRI: they showed a great degree of relatedness.

[Plasmid determined lactose positive character in (Enterobacter hafniae) and (Proteus morganii) (author's transl)]. / Déterminisme plasmidique du caractère atypique lactose positif de Enterobacter hafniae et de Proteus morganii

The atypical lactose positive characters have been found to be plasmidmediated in 6 strains of Enterobacter hafniae and 2 strains of Proteus morganii. One of the P. morganii plasmid possesses the fi+ character, all the other plasmids belonging to the fi-group. Both plasmids of P. morganii could be transduced and remained then readily transferably by conjugation. Two of the E. hafniae plasmids were found unstable when harboured in Salmonella typhi grown at 40 degrees centigrade, when they were stable in the same strain grown at 37 degrees. The other plasmids were stable in the original strains, in S. typhi, in Escherichia coli both at 37 degrees and 40 degrees. These results are discussed according to investigation about (lactose plasmids) of which a bibliographic review is presented here.

[Protective effects of bacterial immunostimulants in mice infected by "Klebsiella pneumoniae" resistant to antibiotics after mutation or by plasmid transfer]. / Immunostimulants bactériens et protection de la souris infectée par Klebsiella pneumoniae résistante aux antibiotiques par mutation ou par transfert de plasmides

A streptomycin-resistant strain of K. pneumoniae obtained after mutation in vitro was found to be less virulent than the sensitive strain in mice. However, a single injection of lipopolysaccharides (LPS) administered 24 hours before challenge increased the host's resistance to both strains. In contrast, the virulence was not changed in K. pneumoniae accepting R-factors for ampicillin, streptomycin, chloramphenicol, tetracycline and sulphonamide. The plasmids were transferred to K. pneumoniae from two strains of Escherichia coli possessing different R-factors with the same resistance pattern. As in the first case, mice pretreated by endotoxin were protected against a challenge by microorganisms carrying R-factors. The capacity of the stimulated host to destory resistant or sensitive organisms was of the same order. Klebsiella recovered 5 or 24 hours after infection from the blood, liver and spleen did not lost their antibiotic-resistance. In this study, BCG and Corynebacterium granulosum were also used. Like LPS, these two immunostimulants protected very effectively mice infected with K. pneumoniae rendered resistant to antibiotics by R-factor transfer.